Telescopic boom

ABSTRACT

A mobile crane has a boom comprising a plurality of telescopic hollow boom sections. Hydraulic operating cylinders for the boom sections are housed within the boom and each is provided with its own remotely operable electrically controlled main valve. Hydraulic fluid is supplied to the valves by flexible hydraulic fluid hoses disposed between the side plates of adjacent boom sections and the hoses uncoil or coil in a frictionless manner as the sections are extended or retracted. Electric control wires for operating the electric wires are wrapped around the hoses and held in place thereon by heat-shrunk plastic tubing. The boom sections have a cross-sectional configuration which is that of an inverted A-frame or trapezoid to increase boom strength, to provide the maximum ratio between internal component space and weight, and to enable a more compact physical arrangement of the boom and boom hoist cylinders on the crane when the boom is in lowered position. The hydraulic cylinders are progressively smaller in size (proceeding from the base end of the boom to its remote end) to provide a balanced hydraulic system and pressure compensating valve means located between the source of fluid and the first (lowest) cylinder respond to pressure differentials thereat to dump or unload excess fluid as is required to maintain a predetermined pressure differential.

United States Patent [191 Wiencek et a1.

[ TELESCOPIC BOOM [75] Inventors: Daniel C. Wiencek; James A. Jones,

both of Cedar Rapids, Iowa [73] Assignee: Harnischteger Corporation,

Milwaukee, Wis.

[22] Filed: Sept. 18, 1972 [21] Appl. No.: 289,986

[52] US. Cl. 212/55 [51] Int. Cl. B661: 23/04 [58] Field of Search212/55, 144; 214/141; 52/115, 118; 91/411 R, 412

[56] References Cited UNITED STATES PATENTS 3,736,710 6/1973 Sterner212/55 X 3,605,561 9/1971 Lado 212/55 X 3,481,489 12/1969 Stauffer212/55 3,633,460 1/1972 Ohniwa et al 212/55 X 3,666,125 5/1972 Gano etal. 214/141 3,489,294 1/1970 Greb et al..... 212/55 X 3,708,937 1/1973Sterner 212/55 X 3,300,060 l/1967 Lado 212/55 3,658,189 4/1972 Brown eta1. 212/55 3,478,894 1 H1969 Stauffer 212/55 OTHER PUBLICATIONS AlphlexShrinkable Tubing (Alpha Ware Corp.) Catalog St-275, see p. 3, CableJacketing.

[111 3,804,262 Apr. 16, 1974 57 ABSTRACT A mobile crane has a boomcomprising a plurality of telescopic hollow boom sections. Hydraulicoperating which is that of an inverted A-frame or trapezoid to increaseboom strength, to provide the maximum ratio between internal componentspace and weight, and to enable a more compact physical arrangement ofthe boom and boom hoist cylinders on the crane when the boom is inlowered position. The hydraulic cylinders are progressively smaller insize (proceeding from the base end of the boom to its remote end) toprovide a balanced hydraulic system and pressure compensating valvemeans located between the source of fluid and the first (lowest)cylinder respond to pressure differentials thereat to dump or unloadexcess fluid as is required to maintain a predetermined pressuredifferential.

10 Claims, 12 Drawing Figures PATENTEBAPR 16 m4 3,804,262

sum 1 or 9 FIG. 1

PATENTEUAPR 16 I974 SHEU 2 [IF 9 PATENTEDAPR s w I 31804262 SHEEI 3 [IF9 PATENTEBAPR 15 mm 3,804,262

sum 5 OF 9 FIG. 6

FIG. 5

PATENTEDAPR 16 m4 SHEET 7 0F 9 PATENTEUAPR 16 1914 saw a [If 9PATENTEBAPR 16 I974 3 804 262 sums 0F 9 FIG. 10

TELESCOPIC BOOM BACKGROUND OF THE INVENTION 1. Field of Use Thisinvention relates generally to booms having a plurality of telescopicboom sections, such as are used on mobile cranes or the like. Inparticular it relates to booms having boom sections of improvedstructural design and having improved means for extending and retractingthe same.

2. Description of the Prior Art Present technology requires that mobilecranes and other equipment employing booms having telescopic boomsections be made increasingly larger and stronger so that the booms canbe extended to greater lengths and can handle heavier loads. Since, forthe practical reasons of cost and reliability, most telescopic boomsections are fabricated from solid sheets or slabs of steel (rather thanof a framework of lighter steel members welded or riveted together), anyincrease in the size of a boom section of conventional design results ina disproportionate increase in weight. This, in turn, results insubstantially greater stress and compression loads being imposed on theboom section components. Therefore, stronger and heavier components areneeded and this. in turn. further increases the overall boom dimensionsand weight. As a result. space and weight considerations become acritical factor in the design of the boom and carriers. Furthermore, asthe overall extended length of the boom increases. larger and longerhydraulic fluid lines are required to supply the hydraulic cylinderswithin the boom and disproportionately larger hose reels are required.

SUMMARY OF THE PRESENT INVENTION In accordance with the presentinvention there is provided a mobile crane which has a boom comprising aplurality of telescopic boom sections. Each boom section is fabricatedof solid steel plates with the top plate being wider than the bottomplate and the side plates welded therebetween and sloped inwardly.Sideplate stiffeners welded between the bottom plate and the side platesrun the length of the boomsection. This configuration results in a boomsection of minimum weight with a bottom plate of relatively increasedbuckling strength and maximum interior space for boom operatingcomponents. Hydraulic operating cylinders for the boom sections arehoused within the boom and each is provided with its own remotelyoperable electrically controlled main valve physically located thereon.Hydraulic fluid is supplied to the valves by flexible hydraulic fluidhoses disposed between the side plates of adjacent boom sections and thehoses uncoil or coil in a frictionless manner as the sections areextended or retracted. A pair of hoses in looped arrangement connecteach pair of adjacent valves. Electric control wires for operating theelectric valves are wrapped about the hoses and held in place thereon byheat-shrunk plastic tubing. A boom inaccordance with the presentinvention is relatively stronger than conventional booms of comparableweight and size, while at the same time enabling a more compactarrangement of boom operating components therewithin. Furthermore. thehoses for supplying hydraulic fluid to the cylinders within the boom aremore simply and compactly arranged. Also, the cross-sectionalconfiguration of the boom sections is that of an inverted A-frame ortrapezoid, and this enables the boom, when lowered, to assume arelatively low position on the crane carrier without the need for widerspacing between the pair of boom hoist cylinders on the carrier whichraise and lower the boom. Other objects and advantages will hereafterappear.

DRAWINGS FIG. 1 is a side view of a mobile crane having a telescopicboom in accordance with the invention;

FIG. 2 is an enlarged view of the interior of the boom shown in FIG. 1with the boom sections shown in partially extended position;

FIG. 3 is another even further enlarged view of the interior of the boomshown in FIGS. 1 and 2 with the boom sections shown in fully retractedposition;

FIG. 4 is an enlarged view of the base of the boom shown in FIG. 1;

FIG. 5 is an enlarged view, with some portions broken away, of one ofthe boom sections shown in FIGS. 1, 2 and 3;

FIG. 6 is a view of the boom section shown in FIG. 5, showing a portionof the rear end thereof and a portion in section on line 6-6 of FIG. 5;

FIG. 7 is an enlarged view of the boom shown in FIG. 3, showing aportion of the rear end thereof and a portion in section on line 77 ofFIG. 3;

FIG. 8 is an enlarged view. partly in cross section, of one of thehydraulic cylinders shown in FIGS. 2, 3, 7 and 9;

FIG. 9 is a schematic diagram of the hydraulic control system for a boomin accordance with the invention;

FIG. 10 is an enlarged cross section view of an electrically operatedhydraulic control valve shown in FIG- URE 8;

FIG. 11 is a top plan view of taken on line 11-11 of FIG. 7 showing thehose connections to the control valve for one of the cylinders; and

FIG. 12 is an enlarged cross section view of one of the hydraulic hosesin the boom showing electrical wires. for the control valves securedthereto.

DESCRIPTION A PREFERRED EMBODIMENT FIG. 1 shows a mobile crane 10comprising a chassis ll, ground wheels 12, an operator's cab 13, ahorizontally rotatable crane upper 14 mounted on the chassis. atelescopic boom 15 in accordance with the invention pivotably mounted onthe crane upper. and a pair of boom hoist cylinders 16 (only one visiblein FIG. 1) connected between the crane upper and the boom.

FIGS. 1, 2, 3 and 7 show that boom 15 comprises a plurality oftelescopic boom sections, namely: a base section 20, an inner midsection 21, an intermediate mid section 22, an outer mid section 23, afly section 24, and a manual section 25. As FIGS. 1 and 4 show. the rearend of base section 20 has trunion mounts 26 on opposite sides whichreceive pins 27 that pivotably mount the base section on crane upper 14.The boom hoist cylinders 16 are located on opposite sides of basesection 20 and are pivotably connected by pins 28 to support brackets 29on crane upper 14. The rod ends of the boom hoist cylinders 16 arepivotably connected by pins 30 to connecting brackets 31 on oppositesides of base section 20. As FIG. I shows, the forward end of manualsection 25 has a working head 32 thereon which, for example, is providedwith a pulley 33.

' As FIGS. 2, 3 and 7 show, the boom also comprises a plurality ofhydraulic cylinders for extending and retracting the boom sections,namely: an inner mid section cylinder 41, an intermediate mid sectioncylin der 42, an outer mid section cylinder 43, a fly section cylinder44 and a manual section cylinder 45. The cylinders operate the boomsections bearing the same name. FIG. 8 is an enlarged view, partly incross section, of outer mid section cylinder 43 and a descriptionthereof will suffice for the cylinders 41, 42, 44 and 45 which areidentical thereto except as regards size. Cylinder 43 comprises a hollowtubular housing 50 closed at one'end by an end plate 51 within which ahollow tubular cylinder rod 52 is slideably mounted. The inner end ofrod 52 is provided with a piston 53 having piston rings 54. Housing 50and rod 52 cooperate to define a cylinder retract chamber'55 and the endof this chamber is closed off by sealing means 56 secured to housing 50and having sealing rings 57. Cylinder rod 52 is provided with a cylinderextend chamber 58. Cylinder rod 52 is also provided with an internalpassage 59 which is connected by a tube 60 to retract chamber 55.Cylinder rod 52 is further provided with an internal passage 61 which isconnected to extend chamber 58. The ports of the passages 59 and 61 areconnected by passages 62 and 63, respectively, in an adapter plate 64 onthe end of rod 52 to ports 75 and 76, respectively,of an electri callyoperated cylinder control valve 67 attached to plate 64. Fluid pressurein passage 61 of rod 52 caused by. extend operation of valve 67 causesfluid flow into extend chamber 58 and effects extend operation ofcylinder 43. Conversely, fluid pressure in passage 59 of rod 52 causedby retract operation of valve 67 causes fluid flow into retract chamber55 and effects retract operation of cylinder 43.

Housing 50 of cylinder 43 is provided on its exterior with a trunnion 68by which it is connected to a trunnion mount 69 on outer mid boomsection 23. Cylinder rod 52 of cylinder 43 is provided on its exteriorwith a trunnion 70, by which it is connected to a trunnion mount 71 onboom section 22. As FIGS. 2 and 3 show, the trunnion 68 on the housingof each cylinder 41, 42, 43, 44 and -45 is connected to the trunnionmount 69 of that boom sectionwhich it operates. The other trunnion 70 onthe rod end of the cylinders 41, 42, 43, 44 and 45 is connected to thetrunnion mount 71 of the next adjacent boom section.

A hydraulic cylinder such as cylinder 43 offers several advantages overconventional hydraulic actuators or cylinders used in prior art cranes.For example, a conventional cylinder is normally connected and supportedat each of its extreme ends (the outer rod end and the base end of thecylinder) to the boom sections I associated therewith. Consequently, inextremely large cranes, as the cylinder is operated to extend the boomsection, the two connection points of the cylinder move very far apartand the cylinder is subjected to buckling and bending forces which tendto increase the risk of mechanical failure of the cylinder'and imposegreater wear forces on internal moving components of the cyl inder. lncylinder 43, however, the attaching and supporting trunnion 70 ofcylinder rod 52 is located near the end of rod 52, whereas the attachingand supporting trunnion 68 of cylinder housing 50 is located near themidpoint of housing 50. Consequently, when cylinder 43 is in retractedor extended condition, the trunnions 68 and 70 are always relativelycloser together than the attachment points of a conventionalcylinder ofcomparable size would be. Thus, cylinder 43 is sub- 5 jected to areduced load and its buckling strength, especially when fully extended,is substantially increased. This factor is of extreme importance inlarger cranes of the type described which have long and heavy boomsections and handle very large loads.

Referring again to FIG. 8, it is seen that cylinder 43 is provided witha conventional h'olding valve 72 which is mounted on plate 64 andoperates to prevent undesired retraction of the extended cylinder untilthe holding valve is released (opened) in response to retract operationof the main control valve 67. Each cylinder 41, 42, 43, 44 and 45 isprovided with a similar holding valve.

The electrically operated main control valve 67 shown in FIG. 10 is anelectrohydraulic proportional metering valve comprising a valve housing73 containing a four-way sliding spool 74, two fluid control ports 75and 76 which are connected through plate 64 to the passages 59 and 61,respectively, in rod 52 of cylinder 43. Valve 67 further comprises anelectrical torque motor 80 and a nozzle flapper pilot stage foroperating spool 74.

The torque motor 80 includes coils 81, polepieces 82, magnets 83 and-anarmature 84. The armature 84 is supported for limited movement by aflexureitube 85. The flexure tube 85 also provides a fluid seal betweenthe hydraulic and electromagnetic portions of the valve.

A flapper 86 attaches to the center of the armature 84 and extends down,inside the flexure tube 85. A nozzle 87 is located on each side of theflapper 86 so that flapper motion varies the nozzle openings.Pressurized hydraulic fluid is supplied to each nozzle through a filter88 and inlet orifice 89. Differential pressures caused by flappermovement between the nozzles 87 are applied to the ends of the valvespool 74.

The four-way valve spool 74 directs flow from pressure supply chamber 92to either control port 75 or 76 in an amount proportional to spooldisplacement. The spool 74 contains flow metering slots 90 in thecontrol lands that are uncovered by spool motion. Spool movementdeflects a feedback wire 91 that applies a torque to thearmature/flappenSpool detent springs 92 are provided to center the spoolwhenever hydraulic driving pressures are absent. I

In operation, electrical current in the torque motor coils 81 causeseither clockwiseorcounter-clockwise torque on the armature 84. Thistorque displaces the flapper 86 between the two nozzles 87. Thedifferential nozzle flow moves the spool 74 to either the right or left.The spool 74 continues to move until the feedback torque counteracts theelectromagnetic torque. At this point the armature/flapper is returnedto center, so the spool 74 stops and remains displaced until theelectrical input changes to a new level. Therefore, valve spool positionis proportional to the electrical signal. The actual flow from the valveto the load will depend upon the load pressure.

A valve such as valve 67 is commercially available from Moog, Inc.,Controls Division, Proner Airport, East Aurora, NY. 14052 and isdisclosed in that companys Catalog 602.

FIGS. 5 and 6 show in detail the physical construction and configurationof intermediate mid boom section 22 which will now be described indetail; it being understood that the other boom sections 20, 21, 23, 24and 25 are similar thereto. Section 22 comprises a top plate 100, abottom plate 101, a right side plate 102, and a left side plate 103.Each of these four plates is fabricated of a solid plate or sheet ofsteel. The upper edges of the side plates 102 and 103 are joined by acontinuous weld to the undersurface of the top plate 100. The loweredges of the side plate 102 and 103 are similarly joined by a continuousweld to the upper surface of the bottom plate 101. Side plate stiffeners105 and 106 are edge-welded between the side plates 102 and 103,respectively, and the edges of the bottom plate 101. The side platestiffeners 105 and 106 serve to increase the buckling strength of theside plates 102 and 103, respectively, by about a factor of five in theembodiment shown. The bottom plate 101 is substantially narrower thanthe top plate 100 (in a ratio of about 5 units to -3 units) and theangle a defined between a side plate and the bottom plate is an anglegreater than 90, but less, for example, than 120. Each side plate 102and 103 is wider than the bottom plate 101 in a'ratio of about 6 unitsto 3 units. Thus, the general cross-sectional configuration of section22 is that of a trapezoid or an inverted A-frame. In a practicalembodiment of the invention, top plate 100 is about 24.6 inches wide,0.375 inches thick, and 383 inches long. Bottom plate 101 is about 13inches wide, 0.500 inches thick, and 376 inches long. Each side plate102 and 103 is about 33 inches wide, 0.l50 inches thick, and 380 incheslong. Each side plate stiffener 105 and 106 runs the length of section22 and is about 6.375 inches wide and 0.250 inches thick. It has beendiscovered through testing that boom section 22 affords the followingadvantages. First, the internal height of boom section 22 is increasedwithout an increase in other cross section properties, such asadditional weight. thereby allowing more internal space foraccommodating components such as the hydraulic cylinders. Second, thestiffener plates 105 and 106 change the end condition of the side plates1 02 and 103 from simply supported to semi-fixed and thereby allowthinner side plates to be used in view of buckling considerations.Third, the relatively narrower bottom plate 101 allows a thinner bottomplate to be used in view of buckling considerations. Fourth, as FIG. 4shows, the relative narrowness of the bottom of aboom section such as 22(particularly boom base section 20) allows the storage position of boomto be lower between the boom hoist cylinders 16 thereby affording loweroverall height without increasing boom section width and'withoutreducing'the moment arm of the boom hoist cylinders. Fifth, the width ofthe top plate 100 of boom section 22 can be varied for desired sidestrength purposes without affecting any of the above-listed advantages.

Referring again to FIGS. 5 and 6, boom section 22 further comprises aslide pad support plate 110 welded to the side plates 102 and 103 at thetop rear end of the boom section. A pair of external slide plate 111 and112 are welded to plate 110 and serve as bearing surfaces for theundersurface of the top plate 100 of the boom section 21 into which boomsection 22 telescopes. Support plate 110 is braced by welded externalbraces 113 and 114 and by a welded horizontal inner brace 115 to whichspaced apart vertical braces 116 are welded.

Rear stiffener plates such as 117 are provided at the rear end of boomsection 22 and are welded to support plate 110 and an associated sideplate 102 or 103.

A cylinder attachment assembly 71 and a trunnion mount 69, bothhereinbefore referred to in connection with the description of cylinder43, are provided at the outer rear end of boom section 22.

Boom section supports, such as support 120, are welded on the innersurface of the side plates 102 and 103-near the rear end of boom section22. Each support 120 is rigidified and stabilized by a brace 121.

A pair of internal slide pads, such as pad 122, are

mounted on a support 123, which iswelded to the inner surfaces of theside plates 102 and 103 near the forward end of boom section 22. Support123 is rigidified and strengthened by a welded horizontal brace 124 andwelded vertical braces 125.

Polyethyle slide pads, such as 130, are mounted on steel backup plates,such as 131," and extend through openings, such as 132, in the sideplates 102 and 103 into the interior of boom section 22 where theyfrictionally engage the sides of boom section 23 which telescopes intoboom section 22. Slide pads 135, similar to project outwardly on thesides of the forward end of boom section 22 for engagement with boomsection 21 into which boom section 22 telescopes.

Referring now to FIGS. 2, 7 and 11, it is seen that the manualsectioncylinder 45, the fly section cylinder 44, and the outer midsection cylinder 43 fit within manual boom section 25 when boom 15 is inretracted condition. Intermediate mid section cylinder 42 and inner midsection cylinder 41 fit within intermediate mid boom section 22 andinner mid boom section 21, respectively. The main control valves 67A,67B, 67 67C and 67D for the cylinders 41, 42, 43, 44 and 45,respectively, 'are supplied with hydraulic operating fluid from apressurized fluid source, such as pumps 136 and 137 shown in FIG. 9,which is understood to be located on crane 10.

FIG. 11 is a top plan view of valve 67 on outer mid cylinder 43 andshows thathydraulic fluid T-fittings 140 and 141 are provided onopposite sides thereof. It is to be understood, for example, thatfittings 140 and 141 are located on the extend sideand the retract side,respectively, of valve 67. Furthermore, valve 67 is provided internallywith a pressure compensated flow control device 142 into which T-fitting140 discharges. The

fittings 140 and 141 on valve 67 are connected by flexible hoses 1498and 1508, respectively, to the pumps 136 and 137 and to a fluidreservoir 147. Thus, hose 149B is for fluid supply and hose 150B forfluid return. The fittings 140 and 141 are also connected to fluidsupply and fluid return hoses 149C and 150C, respectively, which areconnected to the control valve 67C for the next cylinder 44. As FIG. 9shows, the main control valves 67A, 67B, 67C and 67D for the othercylinders are each provided with fluid supply and return T-fittingsdesignated respectively: 140A and 141A; 1403 and 1418; 140C and 141C;140D and 141D. These fittings are interconnected by flexible fluidsupply and return hoses designated, respectively: 149A and 150A; 1498and 150B;- 149C and 150C; 149D and 150D. Thus the main control valvesare connected in parallel arrangement to the fluid supply and fluidreturn systems. As FIG. 9 also shows, the valves 67A, 67B, 67C, and 67Dare provided with pressure compensated flow control devices 142A, 1428,142C and 142D, respectively.

The hydrauliccontrol system shown in FIG. 9 also includes a pressureresponsive valve 156 for automatically connecting pump 137 to the systemif system pressure indicates that more than one cylinder is beingextended and additional fluid is required. The pumps 136 and 137 areunderstood to be engine-driven and operating continuously when crane 10is in use. The hydraulic control system also includes a pressurecompensated flow control valve 157, a pressure switch 158, a reliefvalve 159, and solenoid controlled pressure relief valves 160 and 161.

As FIGS. 2 and 7 show, the flexible fluid supply and fluid return hosessuch as 149C and 150C are physically located between the side plates ofadjacent boom sections in a looped or coiled arrangement which enablesthe hoses to pay out or coil back upon themselves as the boom sectionsare extended or retracted, respectively. As FIG. 12 shows, the lowerportion of each hose loop is supported or rests in support clips 155which are secured at intervals on the outer surfaces of the boom sideplates. It isto be noted that, although each hose flexes at the curvedportion as the boom 15 is operated, the straight upper and lowersegments of the hose do not slide on, rub or frictionally engage thesides of the adjacent boom sections but are stationary with respectthereto. Consequently, the hoses are not subjected to damaging abrasionor wear from this source but only to flexing action.

As hereinbefore explained, the main control valves 67, 67B, 67C and 67Dare electrically operated in response to electric signals supplied tothe torque motor thereon, such as torque motor 80 hereinbefore describedin connection with valve 67. As FIG. 9 shows, each of the fourelectrically controlled main valves is connected by electricalconductors, generally designated 165, which extend from an electricalcontroller 166 on crane 10 to the valves. In practice only twoconductors 165 are necessary for each main valve, although additionalback-up conductors could be provided'for each valve as a safety feature.Furthermore, it is to be understood that controller 166 is designed toenable actuation of each valve separately to allow any single boomsection to be operated individually or to enable actuation of all valvessimultaneously to allow all boom sections to be operated simultaneouslyand proportionately.

As FIG. 10 shows. the electrical conductors 165 for the valves areconnected to a terminal block 167 provided on each valve. Between eachvalve. as FIG. 12 shows. the conductors I65 are twisted around ahydraulic hose. such as hose 149C, and secured in place thereon by meansof a flexible heat-shrunk plastic sleeve or tube 168. Preferably, theconductors 165 take the form of braided insulated wires. Thisarrangement is advantageous'in that the wires are securely held inplace. not liable to damage as the boom sections move, and like thehoses, are not subject to frictional wear but only flexure.

The boom extension cylinders 45, 44, 43, 42 and 41 are sizedprogressively larger from top to bottom so that, although the workingpressure required is least at the uppermost cylinder 45, the combinedeffect of required working pressure, induced load pressure and linepressure drops is such that pressure requirements as measured at thepump 136 or 137, or even at the boom base cylinder 41, are approximatelyequal for any given load, regardless of which cylinder or combination ofcylinders are in use.

It is important to note, as FIG. 9 shows, that there is only onepressure compensated valve 67A, with auxiliary valves, such as 157, forproviding unloading and main relief capabilities near the boom base, fordirectly controlling inner mid section cylinder 41. The other fourvalves 67B, 67, 67C and 67D are remote controlled electro hydraulicproportional metering valves mounted on cylinders in the boom. Inpractice, valve 67A, valve 157, valve 159 and all necessaryinterconnecting tubing are housed in acommon valve housing (not shown).

The pressure compensating valve 157 functions by constantly measuringthe difference between pump and cylinder pressure and dumping orunloading the excess pump flow as required to maintain the desirabledifferential. This would normally be impossible in conventionalhydraulic control circuits for cranes when the most remote cylinderis125 feetaway, but if the system balance is such as is possible in thepresent invention so that the nearest cylinder pressure reading is thesame as the furthest, then it is only necessary to measure and respondto the nearest pressure condition, and the unloading function of valve157 serves the furthest cylinder equally as well as the nearestcylinder.

RESUME A mobile crane 10 has a boom l5 comprising a plurality oftelescopic boom sections 20, 21, 22, 23, 24

and 25. Each boom section is fabricated of solid steel plates with thetop plate being wider than the bottom plate 101 and the side plates 102and 103 welded therebetween and sloped inwardly. Side plate stiffeners105 and 106 welded between the bottom plate 101 and the side plates 102and 103, respectively, run the length of the boom section. Thisconfiguration results in a boom section of minimum weight with a bottomplate 101 of relatively increased buckling strength and maximum interiorspace for boom operating components. Hydraulic operating cylinders 41,42, 43, 44 and 45 for the boom sections 21, 22, 23, 24 and 25,respectively, are housed within the boom and each is provided with itsown remotely operable electrically controlled main valve such as valve67. Hydraulic fluid is supplied to and returned from the valves byflexible hydraulic fluid hoses such as hoses 149C and 150C disposedbetween the side plates of adjacent boom sections and the hoses uncoilor coil in a frictionless manner as the boom sections are extended orretracted. Electric control wires, such as 165, for operating theelectric valves are wrapped about the hoses and held in place thereon byheat-shrunk plastic tubing 168.

Boom 15 in accordance with the present invention is relatively strongerthan conventional booms of comparable weight and size. while at the sametime enabling a more compact arrangement of boom operating components,such as cylinders and hoses, therewithin. Furthermore. the hose meansfor supplying hydraulic fluid to the cylinders within the boom aresimpler and more compact than known hose arrangements.

We claim:

1. In a telescopic boom for use on a machine:

a plurality of relatively movable hollow telescopic boom sections,

each pair of adjacent boom sections defining a space therebetween whentelescoped,

a plurality of hydraulic cylinders mounted within said boom to effectmovement of said boom sections, one cylinder being provided for eachmovable boom section and each cylinder having a portion which isrelatively movable with respect to a portion of a cylinder for anadjacent boom section,

a plurality of remotely operable control valves for operating saidcylinders, each control valve being mounted on the relatively movableportion of its associated cylinder,

a source of hydraulic fluid, v

a plurality of flexible hydraulic fluid hoses for supplying fluid fromsaid source directly to each cylinder, at least one of said hoses beingconnected between the control valves for the cylinders of adjacent boomsections and arranged in a loop located within the space betweenadjacent boom sections when the latter are telescoped,

and control means for remotely operating said control valves.

2. A boom according to claim 1 wherein said control means comprises aplurality of flexible members for effecting operation of said controlvalves, at least one flexible member being coextensive with each hoseconnected between a pair of control valves, and means for securing saidflexible member to a coextensive hose.

3. A boom according to claim 2 wherein said means for securing said'flexible'member to said coextensive hose comprises a heat-shrinkabletubular member around said hose and said flexible member.

4. A boom according to claim 3 wherein said control valves areelectrically operable and wherein said flexible members are electricalconductors.

5. A boom according to claim 4 including a reservoir and at least twohoses connected between the control valves on cylinders of adjacent boomsections, one hose being a fluid supply hose connected to said sourceand the other hose being a fluid return hose connected to saidreservoir.

6. A boom according to claim 5 wherein each hose is disposed in a loopedarrangement in the space between the sides of two adjacent boomsections, and including a support clip mounted on a side of at least oneof said boom sections for supporting said hose.

7. A mobile crane comprising:

an upper portion,

a telescopic boom on said upper portion,

said boom comprising a base section and a plurality of linearly movablesections telescopable therein, each of said sections being wider at itstop side than at its bottom side. each pair of adjacent sectionsdefining a space therebetween when telescoped,

said base section being pivotably connected to said upper portion ofsaid crane for vertical movement,

a pair of boom hoist cylinders for said boom and located on oppositesides thereof, each boom hoist cylinder being connected between saidupper portion of said crane and the base section of said boom, said boomhoist cylinders spaced apart a distance greater than the width of thebottom side of said base section and less than the width of the top sideof said base section.

a plurality of hydraulic cylinders, one for each linearly movablesection, each said hydraulic cylinder being located within said boom andconnected between that section which it moves and an adjacent section,each said hydraulic cylinder having a portion which is relativelymovable with respect to a portion of a hydraulic cylinder for anadjacent section,

a plurality of remotely operable control valves for said cylinders, eachcontrol valve being mounted on the said portion of the cylinder which itoperates,

a source of hydraulic fluid,

and a plurality of hydraulic fluid hoses for supplying hydraulic fluidfrom said source directly to said control valves, at least one hoseconnected between each adjacent pair of control valves and disposed inlooped arrangement in the space between the sides of two adjacentsections when the latter are telescoped.

8. In a telescopic boom having a base end and a remote end:

a plurality of extendable and retractable boom sections, each pair ofadjacent sections defining a space therebetween when telescoped,

a plurality of hydraulic cylinders for operating said boom sections andlocated within said boom,

one cylinder being provided for each movable boom section, each cylinderhaving a portion which is relatively movable with respect to a portionof a cylinder for an adjacent boom section,

said cylinders being progressively smaller in size in proceeding fromthose sections near the base end toward the remote end to provide abalanced pressure system,

a plurality of remotely operable control valves for said cylinders, eachcontrol valve being mounted on the said portion of a cylinder with whichit is associated, I

a source of hydraulic fluid located near the base end of said boom,

means for supplying fluid from said source directly to i the controlvalve for eachof said cylinders, said means comprising a plurality ofhydraulic fluid hoses, at least one of said hoses being connectedbetween the control valves on the cylinders for adjacent boom sectionsand disposed in looped arrangement in the space between adjacent boomsections when the latter are telescoped,

and control means, including pressure compensating relief valve meanslocated near the base end of said boom, responsive to the differentialbetween fluid pressure at said source and fluid pressure of fluid forthe cylinder of the boom section closest to the base of said boom andoperable to unload excess fluid to maintain a predetermined pressuredifferential for said system.

9. A boom according to claim 8 wherein at least some of said remotelyoperable valves for said cylinders are electrohydraulic proportionalmetering valves.

10. A boom according to claim 9 wherein said pressure compensating valvemeans is connected between the source of hydraulic fluid and theremotely operable valve for the cylinder of the boom section closest tothe base of said boom.

1. In a telescopic boom for use on a machine: a plurality of relativelymovable hollow telescopic boom sections, each pair of adjacent boomsections defining a space therebetween when telescoped, a plurality ofhydraulic cylinders mounted within said boom to effect movement of saidboom sections, one cylinder being provided for each movable boom sectionand each cylinder having a portion which is relatively movable withrespect to a portion of a cylinder for an adjacent boom section, aplurality of remotely operable control valves for operating saidcylinders, each control valve being mounted on the relatively movableportion of its associated cylinder, a source of hydraulic fluid, aplurality of flexible hydraulic fluid hoses for supplying fluid fromsaid source directly to each cylinder, at least one of said hoses beingconnected between the control valves for the cylinders of adjacent boomsections and arranged in a loop located within the space betweenadjacent boom sections when the latter are telescoped, and control meansfor remotely operating said control valves.
 2. A boom according to claim1 wherein said control means comprises a plurality of flexible membersfor effecting operation of said control valves, at least one flexiblemember being coextensive with each hose connected between a pair ofcontrol valves, and means for securing said flexible member to acoextensive hose.
 3. A boom according to claim 2 wherein said means forsecuring said flexible member to said coextensive hose comprises aheat-shrinkable tubular member around said hose and said flexiblemember.
 4. A boom according to claim 3 wherein said control valves areelectrically operable and wherein said flexible members are electricalconductors.
 5. A boom according to claim 4 including a reservoir and atleast two hoses connected between the control valves on cylinders ofadjacent boom sections, one hose being a fluid supply hose connected tosaid source and the other hose being a fluid return hose connected tosaid reservoir.
 6. A boom according to claim 5 wherein each hose isdisposed in a looped arrangement in the space between the sides of twoadjacent boom sections, and including a support clip mounted on a sideof at least one of said boom sections for supporting said hose.
 7. Amobile crane comprising: an upper portion, a telescopic boom on saidupper portion, said boom comprising a base section and a plurality oflinearly movable sections telescopable therein, each of said sectionsbeing wider at its top side than at its bottom sidE, each pair ofadjacent sections defining a space therebetween when telescoped, saidbase section being pivotably connected to said upper portion of saidcrane for vertical movement, a pair of boom hoist cylinders for saidboom and located on opposite sides thereof, each boom hoist cylinderbeing connected between said upper portion of said crane and the basesection of said boom, said boom hoist cylinders spaced apart a distancegreater than the width of the bottom side of said base section and lessthan the width of the top side of said base section, a plurality ofhydraulic cylinders, one for each linearly movable section, each saidhydraulic cylinder being located within said boom and connected betweenthat section which it moves and an adjacent section, each said hydrauliccylinder having a portion which is relatively movable with respect to aportion of a hydraulic cylinder for an adjacent section, a plurality ofremotely operable control valves for said cylinders, each control valvebeing mounted on the said portion of the cylinder which it operates, asource of hydraulic fluid, and a plurality of hydraulic fluid hoses forsupplying hydraulic fluid from said source directly to said controlvalves, at least one hose connected between each adjacent pair ofcontrol valves and disposed in looped arrangement in the space betweenthe sides of two adjacent sections when the latter are telescoped.
 8. Ina telescopic boom having a base end and a remote end: a plurality ofextendable and retractable boom sections, each pair of adjacent sectionsdefining a space therebetween when telescoped, a plurality of hydrauliccylinders for operating said boom sections and located within said boom,one cylinder being provided for each movable boom section, each cylinderhaving a portion which is relatively movable with respect to a portionof a cylinder for an adjacent boom section, said cylinders beingprogressively smaller in size in proceeding from those sections near thebase end toward the remote end to provide a balanced pressure system, aplurality of remotely operable control valves for said cylinders, eachcontrol valve being mounted on the said portion of a cylinder with whichit is associated, a source of hydraulic fluid located near the base endof said boom, means for supplying fluid from said source directly to thecontrol valve for each of said cylinders, said means comprising aplurality of hydraulic fluid hoses, at least one of said hoses beingconnected between the control valves on the cylinders for adjacent boomsections and disposed in looped arrangement in the space betweenadjacent boom sections when the latter are telescoped, and controlmeans, including pressure compensating relief valve means located nearthe base end of said boom, responsive to the differential between fluidpressure at said source and fluid pressure of fluid for the cylinder ofthe boom section closest to the base of said boom and operable to unloadexcess fluid to maintain a predetermined pressure differential for saidsystem.
 9. A boom according to claim 8 wherein at least some of saidremotely operable valves for said cylinders are electrohydraulicproportional metering valves.
 10. A boom according to claim 9 whereinsaid pressure compensating valve means is connected between the sourceof hydraulic fluid and the remotely operable valve for the cylinder ofthe boom section closest to the base of said boom.